Shades of Gray: Setting up the Redis Server:

Another limit you may want to consider setting is the maximum memory limit. If you plan to use Redis as a memcached replacement, you will likely wish to control how much memory it can consume. You can set the maximum number of bytes Redis can allocate, after which it will start purging volatile keys. If it cannot reclaim any more memory it will start refusing write commands. Here's a sample setting for a 100MB limit: